Powdered metal components are conventionally manufactured by making a preform which is compacted and then sintered prior to a forging operation. After the forging, any necessary machining of the powdered metal component is performed to complete the manufacturing. Such conventional powdered metal manufacturing has previously been utilized to make piston connecting rod assemblies of the type including a connecting rod and cap. The rod has one end that connects to an associated piston and the cap cooperates with the rod to provide another end that connects the assembly to the crankshaft of the engine in which the piston operates. Such manufacturing of piston connecting rod assemblies whether made from powdered metal forgings or from solid metal forgings requires accuracy in matching of the connecting rod and cap so that a round crankshaft bearing surface cooperatively defined thereby has the required tolerance to permit effective operation for the required lifetime of use.
In order to provide accurate matching of piston connecting rods and caps, the prior art has utilized a fracturing operation for separating a cap from an associated rod at generally diametrically opposite locations with respect to the crankshaft opening cooperatively defined by the cap and the rod. This fracturing provides matched rod and cap surfaces that are subsequently engaged and secured to each other by a pair of cap bolts on opposite sides of the crankshaft opening. Examples of this fracturing are disclosed in U.S. Pat. Nos.: 2,553,935 Parks et al ; 3,818,577 Bailey et al.; and 3,994,054 Cuddon-Fletcher, deceased, et al. Such fracturing provides accurate matching of the engaged cap and rod surfaces without the necessity of any high tolerance machining. However, the fracturing requires considerable energy and care must be taken to maintain the location of the fracture in the required region. See, for example, the aforementioned Bailey et al. patent where heating is performed along the desired band of fracturing by electron beam bombardment and is followed by a subsequent quenching that produces a brittle frangible zone.
Other prior art references include U.S. Pat. Nos.: 1,931,585 Luton; 2,703,263 Zernov; 2,690,004 Crawford; 3,238,811 Longstreth; 3,580,106 Wiehl; 4,030,179 Schwarz; and 4,198,879 Hornak et al.